Alexandrite

Alexandrite is a rare and unique gemstone that was first discovered in 1830 in the Ural Mountains of Russia. What makes this gemstone so unusual is its ability to change color depending on the type of light that it's exposed to. In daylight, alexandrite appears green, blue-green, or yellow-green, while under artificial light, it takes on a reddish-brown or purplish-red hue.

The color-change phenomenon in alexandrite is due to the presence of chromium as an impurity within the mineral. Chromium absorbs certain wavelengths of light and emits them again in a slightly different wavelength, leading to the observed color change.

In terms of its physical properties, alexandrite has a hardness of 8.5 on the Mohs scale, making it relatively hard and durable compared to other gemstones. Its specific gravity ranges from 3.5 to 3.9 g/cm3, which is higher than many other gemstones.

From a geological perspective, alexandrite is found in metamorphic rocks that have been subjected to intense heat and pressure. It forms in the presence of aluminum, beryllium, and chromium, along with other trace elements. The unique combination of geological processes that occur in these areas creates the ideal conditions for alexandrite formation.

Alexandrite is rare gemstone that holds significant value among collectors and jewelry enthusiasts. Its unique color-change phenomenon and geological backstory make it a subject of interest for mineralogists and geologists alike.